Having just received my Cobalt I set up the attachment as per the attached picture. I have the retractor on a "D" ring on my right shoulder and a not retractor on my left. When I am on the beach or my BCD in not on me the SPG or now the computer will be in the non-retractor on my left. When I get the BCD on and am set to dive I will re-clip into the retractor on my right. The computer then sits close at hand on my chest with the hose safely under my left arm pit with my dry suit inflater. I can extend the computer easily for my old eyes to be able to focus or to use the compass.
My set up
YMMV FWIW 
BT
My set up


BT